In the field of internal combustion engines the rotary, or Wankel type engine, as it is often referred to, embodies a number of advantages which make the engine a commercially desirable power plant. Primarily, the relatively simple construction of the engine gives it a significantly reduced bulk and weight for power output. Further, operationally the engine is inherently smooth running due to the unidirectional rotation of the piston. Such motion greatly reduces the degree of vibration and repetitive stress which would ordinarily be experienced in a reciprocating type engine.
However, among the disadvantages which must be tolerated concomitant with the use of the rotary engine, includes the relatively poor fuel economy realized when operated under ordinary circumstances. This penalty in fuel consumption which falls onto the automotive user is found along the entire operating range of the engine.
Further, in view of the desire to minimize the amount of air pollution associated with the operation of any internal combustion engine, the rotary engine is amenable to improvement. For example, under ordinary operating circumstances there will result an exhaust gas from the rotary engine, that is inherently high in HC and CO emissions. Both of these components are found to require relatively complicated control systems if the amount of such emissions is to be reduced to within reasonable ranges.
The rotary engine, as with most internal combustion engines, is limited in the character of the fuel it uses. The latter must be particularly chosen, and carbureted into the engine on an air stream in a manner to form a stoichiometric mixture capable of being easily ignited by a spark source.
Toward affording an improvement in rotary engines whereby the latter will overcome the above noted operational difficulties, and toward permitting use of a greater latitude in the type and grade of fuels which can be burned in the engine, the present invention is disclosed.
The latter includes as a primary objective, the provision of means whereby a number of fuels having minimal octane or cetane requirements can be utilized and efficiently burned in a rotary engine. It further provides means for minimizing the amount of atmospheric pollutants which result from the combustion event in the engine.
Toward meeting the above noted objectives, and providing an improved rotary engine, the instant invention relates to such an improvement wherein the engine includes a casing or housing provided with an internal cavity defined by a trochoidal surface. A rotary piston or rotor comprised of three peripheral faces, is sealably journalled for rotation within the cavity. Each peripheral face, although assuming a generally arcuate configuration, is provided with a shaped compound cavity or depressed pocket.
In one embodiment, a charge fed into the engine during the intake period, compresses air or a suitable mixture of air and other combustibles such as recycled exhaust gas. During the firing period a stream of fuel is forcibly injected into the first of the compound piston cavities. The combustible mixture in the latter, being relatively rich, is immediately ignited in the cavity. The resulting flame, under expanding pressure, is propagated into the second or expansion cavity whereby to ignite the relatively lean charge remaining there.